Sunscreen preparation employing ethylene-maleic anhydride copolymers

ABSTRACT

A gel of the acid form of a cross-linked co-polymer of ethylenemaleic anhydride of the character sold commercially as EMA-91, a sunscreen agent and sufficient of an alkaline reactant compatible with the co-polymer and sunscreen agent to produce a pH in the range of about 5 to 8. The gel vehicle can be water or water and water-miscible alcohol.

United States Patent [191 Black et al.

[111 3,821,363 1 1 June 28, 1974 SUNSCREEN PREPARATION EMPLOYING ETHYLENE-MALEIC ANHYDRIDE COPOLYMERS [76] Inventors: Archie Scott Black, 1323 Broadmoor St., Memphis, Tenn. 381 11; Wolffe Harry Feinstone,

3022 Jackson Ave., Memphis, Tenn. 38103 [22] Filed: Jan. 21, 1971 [21] Appl. No.: 108,610

Related U.S. Application'Data [63] Continuation of Ser. No. 587,968, Oct. 20, 1966,

3/1963 Reinhard 424/78 9/1967 Elermann et a1. 424/59 OTHER PUBLICATIQNS Holzner, Chem. Abstracts, Vol. 60 (1964) p. 1,5351.

Primary Examiner-Albert T. Meyers Assistant Examiner-vincent D. T urncr Attorney, Agent, or Firm-Bruce M. Eisen; Stephen B.

Coan ABSTRACT A gel of the acid form of a cross-linked co-polymer of ethylene-maleic' anhydride of the character soldl c0mmercially as EMA-91, a sunscreen agent and sufficient of an alkaline reactant compatible with the copolymer and sunscreen agent to produce a pH in the range of about 5 to 8. The gel vehicle can be water or water and water-miscible alcohol.

1 Claim, No Drawings SUNSCREEN PREPARATION EMPLOYING ETHYLENE-MALEIC ANHYDRIDE COPOLYMERS This application is a continuation of Ser. No. 587,968 filed Oct. 20, 1966, now abandoned.

BACKGROUND OF THE lNVENTlON preparations which screen much of the ultraviolet rays from sunlight but permit tanning, and those which act to block so much of the ultraviolet sunlight as practically to preclude tanning, for those who are unusually sensitive to sunlight. Sunburn protective products which have been known heretofore are oils, ointments,

greases, creams, cream lotions or alcoholic lotions. Ex-

cept for the alcoholic lotions, these products have left a greasy and sticky film which rubs off easily on clothing, furniture, orv whatever comes in contact with the treated areas of the body. They are likely to be shiny, and to collect dirt and sand, and, coming in contact with the hands, to interfere with the use of the hands. With the exception of very heavy, thick greases, such as red veterinary petrolatum, the suntan or sunblock products, or at least the active sunscreen agents in them, have been easily removed by water so that new applications of the product-are required after one has become wet. People who remainin the water outdoors for some time may become sunbumed because of the loss of the protective sunscreen agent, and the water in. swimming pools is frequently contaminated with sunburn protective products, washed from the body.

Although the alcoholic suntan lotions do not leave. an oily or sticky film on the skin, they are difficult to apply evenly, produce very thin films so that several applications are necessary to provide adequate protection from the sunlight and are easily removed with water.

One of the objects of this invention is to provide a topical sunburn protective preparation which provides protection from actinic rays and permits tanning, but which is easily applied to the skin in a smooth even coating, dries quickly to form a non-oily, non sticky film which is resistant to removal by abrasion, perspiration and water, produces no shine, and lasts longer in use than suntan products known heretofore.

Another object of this invention is to provide preparations that are so effective as to give very high protection from the effects of sunlight to individuals whose skins are especially sensitive to such light, or to individ-- uals who, because of their activities or work, undergo long periods of exposure to sunlight and require extraordinary protection, and yet, unlike oily or thick,

greasy preparations, are un-objectionable for wearing for long periods.

SUMMARY OF THE INVENTION In accordance with this invention, generally stated, a sunburn protective preparation is provided in the form of a gel, which is substantially free from any emulsifying agent or surfactant, which has a viscosity and body which are attractive and enable the user to apply the preparation smoothly and in an even, continuous coat, which dries rapidly and leaves a practically invisible, dry, non-oily, non-sticky film which has remarkable substantivity or endurance. The substantivity of a sunburn protective product may be determined by spectrophotometric measurement of the sunscreen agent in solvent washings of comparable areas of treated skin before and after exposure to water under controlled conditions. By such a test, losses of to percent occur with commercial preparations now in use, as compared'to less than 15 percent with the gels prepared in accordance with this invention.

The sunburn protective preparations of this invention all contain some sunscreen agent compatible with the gel, effective in low concentrations and preferably difficultly soluble in water. Suitable sunscreen agents include esters of paraamino-benzoic acid, e.g., the glyceryl ester, esters of substituted para-amino benzoic acid, e.g., amyl, isoamyl, or ethyl esters of paradimethyl aminobenzoic acid, the ethyl ester of para diethyl aminobenzoic acid and esters of paramethoxycinnamic acid, e.g., 2 ethoxy-ethyl ester. These sunscreen agents may be used in aqueous-alcoholic or aqueous gels. Certain esters of salicylic acid, e.g., homo menthyl salicylate, and certain benzophenone derivatives, e.g., 2-hydroxy-4-methoxy-benzophenone and .2,

I 2-dihydroxy-4-methoxy benzophenone, may be used in lauryl lactate, and moisturizing agents such as propylene glycol, glycerol or polyglycols.

The sunburn protective preparations of this invention can also be made with an insect repelling component, e.g., meta diethyl toluamide, or with the tanning agent, dihydroxy-acetone. When the [latter is used, the gel must have a pH below 5 and must not contain any substance with an active amino group, an amine or ammonia. Esters of substituted para aminobenzoic acid, cinnamic acid or salicyclic acid are suitable sunscreen agents for use in such a preparation.

' The preparations of this invention can be made clear, in which case they are made with an aqueous-alcoholic solution, or they can be made substantially opaque, when they are made with water alone as the vehicle. The alcohol used in the aqueous-alcoholic solution may be any water-miscible alcohol. The gels of the product of this invention are preferably made with cross-linked copolymers of ethylene-maleic anhydride, suitable commercially available forms of which are sold by Monsanto Company under the trademark EMA, as EMA-61, EMA-71, EMA-81, and EMA-91. The molecular weights of these commercial products are all high but increase with the higher numbers. The EMA co-polymers are considered to have the'following formulae:

CHr-CHz-CH-CH p, 0:4. so] O n Anhydride CHr-CHr-CH-CH The cross-linking of the EMA co-polymers is accomplished by reacting across the ethylene backbone (Monsanto Technical Bulletin 1-261, EMA*, page 4). They are available commercially in the form of dry powdered anhydrides, which, in compounding the preparations are suspended in water and converted to the acids, preferably with the aid of heat to hasten completion of the reaction. The resulting solutions are acidic, having a pH of 1.5 to 2.5. The pH is then adjusted to the range of 5-6, to conform to the normal skin condition'by adding an alkali such as sodium, potassium or ammonium hydroxide or an amine such as triethanolamine. When an amine is used the pH of the alcoholic clear gel may be adjusted to at least 7.6. With the opaque aqueous gels, the pH may be adjusted to at least 8 with any of the above alkalis. The addition of the alkali increases the viscosity of the gel. The viscosity of the gel can be controlled within limits by adjusting the amount of the co-polymers. Co-polymers with the higher molecular weights produce a more viscous solution. The viscosity of EMA-61, EMA-71, EMA-81 and EMA-91, in 2 percent aqueous-solution, measured at normal product pH, is 100 Cps, 960 Cps, 1,100 Cps and 8,500 Cps, respectively.

As has been indicated, when the gel contains 45 to 55 percent alcohol by weight (50 to 65 percent by volume), the gel is clear and'transparent. When the gel contains little or no alcohol, it becomes substantially opaque. Both types of gels are stable, and have a long shelf-life.

The Monsanto Technical Bulletin to which reference has been made indicates that although uses for the EMA compounds have been sought since at least as long ago as 1952 US. Pat. No. 2,817,128, page 19 of the bulletin) and although a cosmetic preparation (hair spray) has been patented and EMA-91 used in shampoos and hair sets (id. pp. 16 and 19), its use to form a lotion-like preparation to be applied to and remain on the skin has not heretofore been suggested.

DESCRIPTION OF PREFERRED EMBODIMENTS The following examples are merely illustrative of preparations of the invention.

The co-polymer is suspended in water preferably warm. The mixture is heated on a steam bath (90-95C) with stirring until a thin translucent gel results (-30 min.) when the anhydride is converted to the acid. The gel is cooled to room temperature.

The sodium hydroxide solution Part 2 and the additional water Part 3 are added with stirring. A clear thick gel results. '1'" The components of Part 4 are combined and slowly added to the gel with stirring until completely blended.

A clear viscous gel results.

EXAMPLE 2 Egrt 1 Ethylene-maleic anhydride co-polymcr 91 Methylparaben 0.5 g Water 150.0 cc

Water q.s. 175.25 EM; 3, Amyl p-dimethylamino bcnzoatc 8.75 g Diisopropyl adipate 25.0 g Propylene glycol 10.0 g Perfume 1.0 g Alcohol SD39C Anhydrous 265.0 g Part 4 Y Sodium Hydroxide 5% Solution 15.0 g

Total 500.0 g

The co-polymer is suspended in water, preferably 'warm and heated on a steam bath with stirring until a thin translucent gel results (15-30 minutes) when the anhydride is converted to the acid. The gel is cooled to room temperature and the weight is adjusted by addition of water Part 2.

The ingredients of Part 3 are combined, mixed and added slowly to the gel with stirring.

The sodium hydroxide solution is added with stirring. A clear viscous gel results.

EXAMPLE 3 Part 1 Ethylene-maleic anhydride Co-polymer 91 Methylparaben Propylene glycol Water B LL.

Water Part 3 Glyceryl p-amino benzoate Alcohol SD39C Anhydrous Part 4 Sodium'Hydroxide 10% Solution Total The gel is prepared by the procedure described for Example 2. A clear viscous gel results.

The gel is prepared by the procedure described for Example 2. A clear viscous gel results.

EXAMPLE 5 Bar! 1 Ethylene-maleic anhydride Co-polymer 91 1.0 g Water 30.0 cc PALLL. Water q.s. 38.3 g

e inu d Ea rt 3 Ethyl p-dimethylamino benzoate Diisopropyl adipate Propylene glycol Perfume Alcohol SD39C Anhydrous 5 Ba rt 4 Sodium Hydroxide 5% Solution COMM- Total The gel is prepared by the method described for Example 2. A clear viscous gel results.

The gel of the following example is prepared in the same way. A

EXAMPLE 6 Part 1 Ethylene-maleic anhydride Co-polymer 9| Water Part 2 Water Pagt 3 Ethyl p-diethylamino benzoate Diisopropyl Adipate Propylene Glycol.

Perfume Alcohol SD39C Anhydrous Part 4 Sodium Hydroxide 5% [.0 g 30.0 cc

q.s. 38.3 g

Us 95* PPPE"? oo orooououtm moeoeueon Total Example 7 Part I Ethylenemaleic anhydride Co-polymer 91 Water Part 2 Water Part 3 Amyl p-dimethylamino benzoate l Lauryl lactate 5 Propylene Glycol 2 Perfume 0 Alcohol SD39C Anhydrous 50 Part 4 Sodium hydroxide 5% Solution Total The gel is prepared by the method described for Example 2. A clear viscous gel results.

EXAMPLE 8 R Ethylene maleic anhydride Co-polymer 9| Water Part 2 Water Part 3 Amyl p-dimethylamino benzoate l Myristyl lactate 5. Propylene glycol 2.

Perfume Alcohol SD39C Anhydrous 5 Part 4 Sodium hydroxide 5% Solution Total The gel is prepared by the method-which is described for Example 2. A clear viscous gel results.

EXAMPLE 9 Part 1 Ethylene-maleic Anhydride Co-polymer 7l Water Par; 2 Water 2.0 g 30.0 cc

q.s. 37.3 g

The gel is prepared by the method which is described in Example 2. A near clear viscous gel results.

EXAMPLE 1 0 Part I Ethylene-maleic anhydride Copolymer 81 Water fig rt 3 Water Pgrt 3 Amyl p-dimethylumino benzoate Diisopropyl adipate Propylene Glycol Perfume Alcohol SD39C Anhydrous r 5 Pan 4 Sodium hydroxide 5% Solution q.s. g g

ONCCUI 8 E g E 8 i 4. g l00.0g

Total The gel is prepared by the method described for Example 2. A clear .very viscous gel results.

EXAMPLE 1. 1

Part 1 Ethylene-maleic Anhydride Co-polymer 91 Water Part 2 Water Part 3 Amyl p-dimethylamino benzoate Di-isopropyl adipate Propylene Glycol Perfume Alcohol SDA 39C anhydrous Part 4 Triethanolamine I 1.0 g. 25.0 cc

l8.57c solution once Total This gel is prepared by the method which is described for Example 2. A clear viscous gel results.

EXAMPLE 1.2

Part] Ethylene-maleic anhydride Co-polymer 91 Water Part 2 Water Part 3 Amyl p-dimethylamino benzoate Diisopropyl adipate Propylene Glycol Perfume Alcohol SD39C Anhydrous m Potassium hydroxide 7% VI PPPYT co ONOOU: w 00 neg commence on Total The gel is prepared by the method which is described for Example 2. A clear viscous gel results.

EXAMPLE l3 Ethylene-maletc anhydnde (Io-polymer 9l [.0 g Water 30.0 cc

Water q.s. 39.3 g

Continued Continued Pg rt 3 Amyl pdimethylamino benzoate 1.5 g Diisopropyl adipate 5.0 g Em I Propylene glycol g Ethylencmaleic anhydride Co-polymer 91 1.3 g Perfume g 5 Water 20.0 cc Alcohol SD39C Anhydrous 50.0 g gm 2 M 0 Water q.s. 26.0 g Ammonlum hydroxlde Solutlon (2.13% NH 2.0 g Em Tmul moo g Amyl p-dimcthylumino hcnmatc 1.6 g M cta-diethyl toluumidc 10.0 g The gel is prepared by the method which is described E' ll'gt g for Example 2. A clear viscous gel results. Alcohol $0390 95% 52.7 g

EiLLLL EXAMPLE [4 Sodium hydroxide 5% Solution 2.5 g

Total 100.0 g

p n 1 I The gel is prepared by the method described for Ex- Ethylene-maleic anhydride -p y 91 g ample 2. A clear viscous gel results. Water 30.0 cc EXAMPLE l8 Suntan-Insect Repellent Gel Water q.s. 39.3 g Part 3 Amyl p-dimethylamino benzoate 1.5 g Diisopropyl adipate 5:0 g Part 1 Propylene glycol 2.0 g Ethylenc-maleic anhydride Co-polymer 91 1.1 g. Perfume 0.2 g Water 25.0 cc. Alcohol SD39C Anhydrous 50.0 g Bart 2 Part 4 Water q.s. 27.41 g. Triethanolamine 18.5% Solution 2.0 g Part 3 Total 100.0 g Amyl p-dimethylamino benzoate 1.75 g. Insect Repellent MGK5579* 10.0 g. Pro lene GI col 2.0 The gel 18 prepared by the method described for Exgl y 01 g ample 2. A clear viscous gel results. 3 2 SDA 39B art Di-isopropanolamine 16.6% solution 6.00 g. EXAMPLE 15 Total 100.00 g.

lnsect Repellent MGK5579 contains: pan 1 N, Diethyl-meta toluamide 4071 Ethylene-maleic anhydride Co-polymer 91 I 68.0 g Noclyl bwycloheptene dlcal'boxamlde 40% Water 20000 cc 2, 3, 4. 5 Blx (Abutylene) Pan 2 tetrahydrofurfural 10% Water 2300 CC 35 Di-n-Propyl isocinchomeronate 1071 ELL. 35 f gi i ig' 88: The gel is prepared by the method described for Expropylleneyglycol 136:0 g ample 2. A clear viscous gel results. Perfume 13.6 g Alcohol SD39B 95% 4550.0 cc 4o EXAMPLE 19Suntan-dlhydroxyacetone Quick Part 4 T i Color concentrate (Caramel) 5.4 g ng Part 5 Sodium hydroxide 5% Solution 270.0 cc

. Total 2 gal. (7560 cc or 6800 g) Part 1 v Ethylene-maleic anhydride Co-polymer 91 6.0 g Water 150.0 cc The gel 15 prepared by the method descrlbed for Exp 2 ample 2. The caramel color was added before the Y q- 161-6 0 n drum hydroxide with stirring. A clear, amber, VISCOUS pdmflhylamino benwale 60 g gel results. Diisopropyl adipate 16.0 g Propylene glycol 8.0 g EXA PLE 16-Sunblock Gel Perfume g M 50 Alcohol SD39C Anhydrous 189.6 g

Part 4 Dihydroxyacetone 14.0 g Part 1 Part 5 Ethylene-maleic anhydride Co-polymer 91 34.0 g Sodium hydroxide 5% Solution 7 4.0 g Water 1 150.0 cc Total 400.0 g Part 2 1 1218.2 l q S g The el is re ared b the method described for Ex- Part 3 g y g y phy benloate 10210 g ample 2. The dlhydroxyacetone 15 added to the gel beg sg g z ffig 238; fore the sodium hydroxide with stirring unitl solution is Perfume 6.8 g complete. The near clear. viscous gel, pH 4.2 results. Alcohol SD39C Anhydrous 2160.0 cc Part 4 Sodium hydroxide 5% Solution 135.0 cc

Total 1 gal. (3780 cc or 3400 g) EXAMPLE 20 Opaque Suntan Gel The gel is prepared by the method descrlbed for Ex- P I ample 2. It contains 3 percent sunscreen, amyl p- Ethylene-maleic anhydride Co-polymer 9| 0.6 g. dimeth lamino benzoate. y P l Gl l 2 0 ropy ene yco g. 1. "l 31 9l R? .c Methylparaben 0.17 g.

Continued Propylparaben Part 3 Water q.s. 87 Part 4 Homo-menthylsalicylate 8 Perfume 0 Part 5 Sodium hydroxide 5% solution 4 Total 100.

The co-polymer is suspended in water. The mixture is heated to.90-95C with stirring until a translucent solution results (20-30 minutes). The solution is cooled to room temperature.

The parabens in Part 2 are dissolved in the propylene glycol and the solution is added to Part I. v

The weight of the mixture is adjusted by addition of water.

The ingredients in Part4 are combined and mixed and the solution is slowly added to the gel with stirring. The sodium hydroxide solution is added slowly with vigorous stirring. The gel mixture is homogenized to give a white smooth viscous opaque gel.

EXAMPLE 2l-Opaque Suntan Gel anhydride Co'polymer 91 Homo'menthylsalicylate Perfume Part 5 Sodium hydroxide 5% solution w PW? P wer The opaque gel is prepared by the method described for Example 20. A white viscous gel results.

EXAMPLE 22 Opaque Sunblock Gel Part 1 Ethylene-maleic anhydride Co-polymer 9| 0.6 g. Water 50.0 cc. Part 2 Propylene Glycol 2.0 g. Methylparaben 0.17 g. Propylparaben 0.03 g. Part 3 Water q.s. 88.55 g. Part 4 Amyl p-dimethylumino benzoate 2.75 g.

Homo-menthylsalicylate 4.00 g.

Perfume 0.2 g

Sodium hydroxide 57: solution 4.5 g.

Total I00 The gel is prepared by the method described for Example 20. A white viscous gel results.

EXAMPLE 23 Sunblock Opaque Gel ELL Ethylene-maleic anhydride Co-polymer 9! The opaque gel is prepared by the method described for Example 20. Part 4 may be warmed to hasten solution. A light yellow viscous gel results.

. 'We claim:

g l. The method of providing protection for the skin of a human body from the actinic rays of the sun comprising applying to the skin smoothly and in an even, con-.

tinuous coat a sunburn protective preparation which dries rapidly and leaves a practically invisible, dry, nonoily, non-sticky film which has remarkable substantivity or endurance, said sunburn protective preparation comprising a major proportion, sufficient to provide a film on the human body, of a gel, in a vehicle selected from the group consisting of water and an aqueous solution of watermiscible alcohol, of the acid form of a cross-linked co-polymer of ethylene-maleic anhydride having a viscosity, in a 2 percent aqueous solution having a pH of 1.5 to 2.5, of about cps,.960 cps, 1,100 cps or 8,500 cps; and an effective amount of a sunscreen agent compatible with the gel, and sufficient of an alkaline reactant compatible with said co-polymer and sunscreen agent to produce a pH in the range of about 5 to 8. 

